This invention relates to the segmentation of different phases or states in solids and, more particularly, to the segmentation of pores and minerals in sections of reservoir rocks.
The invention of this application relates to the subject matter of our co-pending application entitled "Analysis of Reservoir Pore Complexes," Ser. No. 524,022, filed Aug. 17, 1983, now abandoned in favor of 16,495.
As disclosed in our co-pending application, petrographic image analysis relates to the characterization of images obtained with a transmitted light microscope from 30 micron petrographic thin sections whose pores are impregnated with blue-dyed epoxy. The thin sections scene is digitized through red, green and blue filters having known spectral characteristics. The filters provide the maximum enhancement to the blue-dyed epoxy-filled pores while leaving the background mineral matrix of non-pores relatively unchanged. A blue dye is chosen because there are few, if any, naturally occurring blue constituents within reservoir rocks.
The mode of illumination is transmitted light rather than reflected light. This results in a scene with a high range of intensity as well as, generally, a high average intensity. Except for those representing opaque objects, most of the pixels have relatively small variation in the intensity values of the three primary color components. Segmentation based on intensity values alone, as disclosed in application Ser. No. 524,022 can lead to misidentification of pixels representing pores and pixels representing non-pores.
Segmentation of pores for the purpose of petrographic analysis must not only identify the pores but precisely define the edges of the pores in order to assure that such features as pore geometry and pore proportion are accurately measured. Segmentation must also be accomplished quickly because many thousands of scenes, each containing as many as one hundred or more pores, must be processed in a typical investigation.
Also, it is desirable that only the portion of the pore that is on the surface of the thin section be identified as a pore in the segmentation process. Because thin sections have a defined thickness, there is often a shelving effect where the edge of the pore is underlain with or overlain by mineral material. Differentiation between the two different types of shelves is necessary to assure that only the pore overlaying the shelf is segmented along with the solid pore.
Prior art segmentation techniques are described in the following articles and publications:
1. R. Ohlander, K. Price, and D. R. Reddy, Picture Segmentation Using a Recursive Region Splitting Method, Comp. Graph. and Image Proc., 8, 1978, 313-333.
2. M. Goldberg and S. Shlien, A Four-Dimensional Histogram Approach to the Clustering of LANDSAT Data, Canadian Journal of Remote Sensing, 2, 1976, 1-11.
3. B. J. Schacter, L. S. Davis, and A. Rosenfeld, Scene Segmentation by Cluster Detection in Color Spaces, SIGART Newsletter No. 58, 1978, 16-17.
4. R. B. Ohlander, Analysis of Natural Scenes, Department of Computer Science, Ph.D. Thesis, Carnegie-Mellon University, 1975.
5. A. Ruter, H. Harms, and H. M. Aus, Standardized Color Measurement in Automated Cytophotometry with the Light Microscope, Pattern Recognition, 13, 1981, 135-323.
6. Y. Ohta, T. Kanade, and T. Sakai, Color Information for Region Segmentation, Comp. Graph. and Image Proc., 13, 1980, 222-241.